#include<iostream>
#include<cstdio>
using namespace std;
long long  sum;
int main()
{
	int n;
	int count = 0;
	while (scanf_s("%d", &n)!=EOF) {
		count++;
		sum += n;
	}
	long long a = 1;
	for (int i = 0; i < count - 1; i++) {
		a *= 2;
	}
	sum *= a;
	cout << sum << endl;
	return 0;
}